Magnonics—magnetic analogue to photonics—is amongst the promising post-complementary metal-oxide semiconductor (CMOS) computing technologies in which the spin waves (SWs) or magnons (quanta of SWs) carry the information instead of charge. Significant progress has been made towards the practical realization of magnonic devices in-terms of on-chip generation, directional channeling, detection and manipulation of SWs. One of the building blocks of any magnonic devices is the waveguide that transmits SWs from one physical location to another. Waveguides in the form of micro-stripes or wires are generally used in proof-of-principle nanomagnetic devices where the SW propagation is limited by the material dependent Gilbert damping. The SW decay length varies from several microns to few tens of microns in the commonly used materials such as Ni80Fe20 (Permalloy), Heusler alloy, CoFeB and Yttrium Iron Garnet (YIG).
Magnetostatic surface SWs or the Demon-Eshbach (DE) SW modes which propagate perpendicular to the in-plane magnetization direction, are promising in this context due to their large group velocities (vg), low attenuation and suitability for experimental implementations. Consequently, in a typical micro-strip waveguide, a large external bias magnetic field (typically 500-1200 Oe) is used to force the magnetization to orient perpendicular to the SW propagation direction. This is a major obstacle for implementing such waveguides into a practical device. Also, such global external field does not support DE configuration for transmitting signal through a curved waveguide which was later addressed by utilizing the Oersted field generated from an underlying current carrying stripe that may also be used for straight waveguides. Although waveguides with underlying current lines may in principle be integrated into a device for on-chip biasing, it will continuously draw power and the heat generated in a dense circuit could inhibit the benefits of a magnonic device which promises to deliver ultra-low power computing. Therefore, an alternative energy-efficient approach for SW transport in straight as well as curved waveguides is desired. Recently, it has been shown theoretically that SW transmission through bents is possible using domain walls in ultrathin ferromagnetic films.
Another important element to obtain digital functionalities is the local manipulation of amplitude and/or phase of the propagating signal. Several methodologies have been adopted which include the use of magnetic field inhomegenity, non-linear SW properties, dynamic magnonic crystal (MC), variation of local magnetization orientation, SW phase manipulation. Thus, a waveguide with a simple design and energy-efficient local manipulation mechanism can be of significant technological importance.
Embodiments of the present invention seek to address one or more of the above-mentioned needs.